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VB2005实现UDP通信例程

时间:2010-04-27 01:03来源:未知 作者:admin 点击:次

Imports System.Threading

Imports System.Text
Imports System.Net.Sockets
 Module Module1
     Dim PortNumber As Integer = 1984    '侦听端口号
    Dim Cmd As String = "Chat:"         '提示符
    Dim listener As Socket              '侦听socket
    Dim tListener As Thread             '侦听线程
    Dim Prompted As Boolean = False     '用于线程间同步的标志变量
     Sub Main()
        Welcome()                       '欢迎信息
        StartListener()                 '开始侦听
        StartChatting()                 '准备好让用户发送消息
    End Sub
     Private Sub Welcome()
        Dim txtMessage As String = vbCrLf & "Welcome! I am a console application for LAN chatting." & vbCrLf
        Console.WriteLine(txtMessage)
    End Sub
     Private Sub StartListener()
        Dim ready As Boolean = False
        Dim LocalPoint As IPEndPoint
        Dim msg As String
         While Not ready '向用户询问侦听端口号。用户可以直接回车，表示选择默认的。
            msg = GetParams("===Now, enter the local port you want to listen(" & PortNumber & "):")
            If msg = "" Then msg = PortNumber
            Try
                PortNumber = Int(msg)
                LocalPoint = New IPEndPoint(Dns.GetHostByName(Dns.GetHostName).AddressList(0), PortNumber)
                listener = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)
                listener.Bind(LocalPoint)
                ready = True
            Catch ex As Exception
                Console.WriteLine("※※※ERROR※※※ " & vbCrLf & ex.Message & vbCrLf)
            End Try
        End While
         tListener = New Thread(AddressOf thrListener)
        tListener.Start()
    End Sub
     Private Sub StartChatting()
        Dim RemoteHost As String = Dns.GetHostName
        Dim RemotePort As Integer = 1984
        Dim RemotePoint As IPEndPoint
 Dim ready As Boolean = False
        Dim msg As String
         While Not ready '向用户询问发送消息的目标主机和端口。用户可以直接回车，表示选择默认的。
            msg = GetParams("---enter the name of the one you want to chat with(" & RemoteHost & "):")
            If Not msg = "" Then RemoteHost = msg
            msg = GetParams("---enter the port number that guy listening at(" & RemotePort & "):")
            If msg = "" Then msg = RemotePort
            Try
                RemotePort = Int(msg)
                RemotePoint = New IPEndPoint(Dns.GetHostByName(RemoteHost).AddressList(0), RemotePort)
                ready = True
            Catch ex As Exception
                Console.WriteLine("※※※ERROR※※※ " & vbCrLf & ex.Message & vbCrLf)
            End Try
        End While
         Console.WriteLine()
        Console.WriteLine("OK, now you can chat. Type ""help"" to find out what you can do.")
        Console.WriteLine()
         Dim sender As New UdpClient
        Dim Message As String = Prompt()
        While True      '用户现在可以开始发送消息
            Prompted = False
            Select Case Message.ToLower
                Case "exit"
                    Exit While
                Case "help"
                    ShowHelp()
                Case Else
                    Dim ByArr As Byte() = Encoding.Unicode.GetBytes(Message)
                    sender.Send(ByArr, ByArr.Length, RemotePoint)   '发出消息
            End Select
            Message = Prompt()
        End While
         tListener.Abort()
        End
    End Sub
     Private Function GetParams(ByVal Msg As String) As String
        Console.Write(Msg)
        Return Console.ReadLine
    End Function
 Private Function Prompt() As String
        If Not Prompted Then
            Console.Write(Cmd)
            Prompted = True
        End If
        Return Console.ReadLine
    End Function
     Private Sub thrListener() '侦听线程
        Dim bytes(4096) As Byte
        Dim NumGet As Integer
        Dim Msg As String
         While True
            Debug.WriteLine("Waiting for a message...")
            NumGet = listener.Receive(bytes)   '接收
            Prompted = False
            Msg = Encoding.Unicode.GetString(bytes, 0, NumGet) '与发送消息一样使用unicode编码
            Console.WriteLine(vbCrLf & ">>>>>>>>>" & Msg & vbCrLf)
            If Not Prompted Then
                Console.Write(Cmd)
                Prompted = True
            End If
        End While
    End Sub
     Private Sub ShowHelp()
        Console.WriteLine("")
        Console.WriteLine("========================================================================")
        Console.WriteLine("This program is very simple, you can type ""exit"" to exit program.")
        Console.WriteLine("========================================================================")
        Console.WriteLine("")
    End Sub
End Module
(责任编辑：admin)
Tags：VB2005
责任编辑：admin
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